Steam cylinder oil and process of preparing the same



Patented Feb. 11, 1 941 UNITED STATES "PATENT OFFiCE STEAM CYLINDER OIL AND PROCESS OF PREPARING THE SAME ration of Delaware No Drawing.

Application June 11, 1937,

Serial No. 147,784

2 Claims.

uses of such oils.

Steam cylinder oils may not be supplied to the walls of the pistons and cylinders of the engine in many of thewell-known forms of lubrication, but are introduced to the cylinders with the steam in such fashion that they are finely divided by atomization, whereby they are spread evenly over the moving parts.

In the modern steam engine practice the temperature of the steam in the cylinder of the engine when closed by the piston goes as high as 500 F., under its corresponding pressure, and under such conditions it is highly important not only that a proper distribution of the oil is assured, but also that the stability of' the oil is such as to resist decomposition, whereby undesirable deposits, such as coke, and thelike, are eliminated.

Oils which have'a tendency to emulsify with steam are best suited for steam cylinder oils and heretofore it has been common practice to compound with a mineral oil a certain percentage of a fatty oil, such as tallow, which causes emulsification. Such fatty oil, or oils; usually represent up-to 8% to 10% of the mineral oil, but in addition to being costly, are decomposed at high temperatures which do not affect the mineral oil hydrocarbons thus forming free fatty acids which attack metals under such temperature conditions.

The problemsof steam cylinder lubrication are thus inherently different from the problems pt lubricating the cylinders of internal combustion engines-due to operating conditions at high temperatures and pressures in the presence of water I vapor, which factors require that the cylinders be preferentially wet with the oil rather than with the water.

For this reason, high viscosity oil have been found best suited for steam cylinder lubrication and such oils should be processed for emulsification with the steam used in order to provide the desired preferential wetting of the cylinderwith oil.

Although high viscosity oils are generally applicable to steam cylinder lubrication, this factor is not necessarily limiting as the invention involves the preparation of an oil which will provide adequate lubrication while possessing an inherent quality of stability under severe conditions of high temperature and in the presence of steam.

Thi invention provides a way of insuring the stability of steam cylinder oils while emulsifying the same under operating conditions, which is preferably accomplished in the following manner.

As a base stock for steam cylinder oils it is preferred to select a lubricating oil which is composed mainly of saturated hydrocarbons, such oil, for example, being an asphaltic base, or mixed base, oil, which is highly refined by treatment with liquid sulphur dioxide, as in the well-known Edeleanu process, to remove unsaturated hydrocarbons, aromatics, etc.

Such lubricating oil, thus treated, shows the greatest stability under high heat conditions, but, of course, a body of saturated hydrocarbons may also be prepared by extensive sulphuric acid treatment, or even distilled from certain stocks, such as Pennsylvania crudes.

It ha been found, however, that certain oils I of less saturated character can be stabilized by the processing method herein described. Such oils may include distillates from asphaltio or mixed base crudes, as Well as lubricating oils obtained from such distillate by comparatively mild refining operations, such'as the conventional acid treatment.

To the base lubricating oil is added a polyvalent metal soap, as lime or magnesium soap, of an organic acid, such for example as oleic acid, stearic acid, palmitic acid, naphthenic acids, or sulphonic acid, the proportion of such added soap ranging from very small percentages of the oil, e. g., .01% to .1%, up to the limit ofsolubility of said soap in said oil.

The alkaline earth metals, calcium, strontium, barium, and magnesium, yield soaps with organic acids which exhibit suitable stabilizing qualifications. When such soaps of a stable nature are added to oils, the resistance of the lubricant to decomposition, particularly under the high temperatures encountered in steam cylinder lubrication and other services, is greatly improved, and as a feature necessary for steam cylinder lubricationwe again emphasize the necessity of a stable compounded lubricant as heretofore outlined.

We have found that the "alkaline earth metal soaps do not form incrustations in service and of these calcium and magnesium soaps are preferred for economical reasons. However, the soaps of cadmium, aluminum, zinc, lead, copper, chromium, manganese, iron, cobalt, nickel, tin and mercury, may also be used.

- Any organic acid which will yield a polyvalent 5 metal soap with suitable stabilizing properties,

is applicable to the process. Fatty acids, for example, oleic, stearic, palmitic, and derivatives of the same, have been successfully employed. Of the fatty acids we prefer to use those of fourteen or more carbon atoms. Normally the more saturated acids, as stearic and palmitic, yield soaps which are less soluble in oil than the unsaturated acids, e. g., oleic, but a saturated acid of excellent solubility may be obtained through the hydrogenation of unsaturated acids of certain types. To illustrate; unsaturated acids from fish oil when hydrogenated, yield acids which can be made into polyvalent metal soaps having superior oil'solubility' properties. The acids from fish oils may be obtained in large quantities by splitting the esters normally present therein.

Polyvalent metal soaps of the hydrogenated acids derived as above described are soluble in oil up to 5 per cent by weight, and are very efilcient stabilizing agents. V Sulphonic acid soaps are very soluble in oil.

Acids of this type. which have been found particularly suitable, may be derived from the sulphonation of 80 to 200 seconds, Saybolt Universal 100 F., oils of asphaltic origin, or raflinates derived therefrom by the well known Edeleanu treatment with liquid sulphur dioxide. Also from the extracted portion of the Edeleanu treatment aromatic type sulphonic acids may be prepared, from which suitable polyvalent alkaline earth or other metal aromatic sulphonic acid soaps can be made for the described purpose.-

Polyvalent metal soaps of ,the naphthenic acids are normally more oil soluble than those of the 4o fatty acids, and are excellent stabilizing and emulsifying agents. Of the naphthenates those I of calcium, magnesium, tin, and aluminum are preferred.

' Depending largely on the degree of emulsification and the stabilizing influence desired, the content of soaps dissolved in the oil may vary from a minute amount up to the limit of oil solubility. The following table is illustrative of the solubilities' of the calcium soaps in the oil.

. 50 TABLE I Solubility in smal 011,8

Calcium sulphonate 50% or more... 50% or more. Calcium naphtbenate 4% max l0% max. Calcium oleate 0.5% max"... 1% max. Calciumstearate 0.27 max 0.4% max. Calcium palmitate 0.1 max 0.3% max.

The above soaps arelisted in the order of:

Decreasing solubility in oil.

Increasing qualifications as lubricant stabilizers,

65 Decreasing emulsifying properties.

A table similar to the above can be prepared for magnesium soaps which have similar properties to the respective calcium soaps except they are in general slightly more soluble in oil and not 70 quite as stable.

Aluminum soaps of organic acids show excellent solubility in mineral oils of all types. However, when added in percentages in excess of about 2%, the compounded oils possess a stringy 76 structure, which for our purpose is undesirable.

The preferred range for aluminumsoaps is between 0.01% up to 1.0% by weight of the oil.

In the preparation of lubricants we have also found that the solubility of the less soluble polyvalent metal soaps can be increased by the mixing therewith of a more soluble soapof polyvalent metals. For example, the solubility of calcium oleate can be tremendously increased by the simultaneous incorporation in the lubricant of a comparatively-small percentage of a more soluble calcium or other polyvalent metal soap, such as calcium naphthenate or calcium sulphonate. This is a particularly important feature' when it is desired to permanently incorporate in the oil soaps of relatively low solubility. The. following table clearly illustrates this feature, and it should be noted that the solubility of calcium oleate in the same oil and under the same conditions has been increased many fold by the addition of a small percentage of a more soluble soap.

TABLE II Solubility of calcium oleate in California lubricating oil Per cent Calcium oleate 1.0 Calcium oleate+10% calcium naphthenate 2.5 Calcium oleate+20% calcium naphthenate 4.0 Calcium oleate+30% calcium naphthenate 7.0

Although in the above example calcium naphthenate has been shown because of its well known oil solubility feature, this in no way should be indicated as a limitation on this feature, and a similar result is obtained by the use of other more soluble soaps, such as the polyvalent metal soap of sulphonic acid.

In describing this invention which is particularly directed towards the manufacture of a steam cylinder oil of stable oil and soap characteristics, it is important that a permanent solution of soaps be incorporated in the oil. Therefore, in order to increase the total soap content for this or other possible lubrication purposes, ithas been found advantageous to utilize'stable soaps made from a mixture of acids.

In order to provide the maximum stability to resist the high temperature conditions encountered, and still provide enough soap for proper lubrication in conjunction with steam or otherwise, such emulsiiiable oil should contain a maximum quantity of'the preferred soaps described herein.

Thenovel feature of mixing two or more soaps is utilized when it is desired to increase the solubility of the more insoluble polyvalent metal soaps in oil over the maximum noted in Table I.

The following table is illustrative of the quantitles of polyvalent metal soaps normally added to the oil and the preferred-range of soap content for the steam cylinder oils.

It is important in the application of the above ranges of soap content to lubricants to add just sufficient soap to give the desired stabilization properties. In steam cylinder oils the addition is such as to give the desired emulsifying properties and, prevent the formation of incrustations or deposits on the cylinder walls of the lubricated mechanism. In general the addition is so small that the amount of ash arising from its use as an emulsifier is too small to be determined analytically.

The use of soap results in a steamcylinder oil of unimpaired stability which emulsifies sufliciently to get the desired distribution, the soaps being easily combined with the saturated hydrocarbons, due to their oil solubility.

Likewise, a steam cylinder oil having the required emulsifying properties may be prepared from oils which result from the distillation of a suitable crude stock and which may be naturally composed mainly of saturated hydrocarbons.

For instance,.,residual oils of Pennsylvania origin when traces of oxides, or hydroxides, are added to the oil when heated, such oil develops the de sired pronounced emulsifying properties. To such oils, an organic acid or acids not normally present in petroleum may be added, and the requisite amount of polyvalent' metal oxide or hydroxide, to accomplish of the oils, applied.

A preferred amount of polyvalent metal oxide or hydroxide, for example, magnesium oxide, or lime, or other alkaline earth oxide, or hydroxide, which may be added to such residual oil varies from 0.01% to 0.1%, and such isincorporated in the oil by intimate mixing at elevated temperatures, preferably about 300 F., and generally in excess of atmospheric temperatures. This oil may then be used as straight steam cylinder oil, or may be blended in amounts of from 10% to 20% with a body of a highly refined oil of high stability, such as the S02 treated oil previously described.

The soaps may be added directly to the oil, during agitation either mechanically or with air, and the oil heated to 200-300 F. The preferred method however, is to first dissolve the desired quantity of organic acid in the oil and slowly add a metallic oxide 01' hydroxide, of the polyvalent substantial neutralization metalspreviously cited, heating preferably to about 300 F., and generally in excess of atmospheric temperature, and agitating the mixture until neutralization of the free acid is substantially complete. In such manner the soap is more readily incorporated in the oil and excellent dis-' tribution and dispersion of thesoap in the oil is accomplished. When prepared in this manner with excess quantities of acid and oxide the quantity of the soap which is retained in the oil represents the maximum of solubility. This oil may be used as is, or blended in amounts from 10% to 50% with additional quantities of suitable base oils.

While it is unnecessary, the use of small amountsof an acidless fatty oil with the steam cylinder oils prepared as above described, has sometimes a beneficial effect in lowering the surface tension, but the quantity used, from 0% to 3%, is kept as low as possible and in any event is far less than the amount normally u'sed'in compounding steam cylinder oils.

This application is a continuation in part of our two copending applications, now Patents 2,084,531-2.

We claim as our invention:

1. A process of preparing an emulsifiable oil suitable for use in the cylinders of steam engines which comprises, mixing a percentageof a polyvalent metal soap of an organic acid of the group consisting of fatty acids of 14 or more carbon atoms, andoil soluble sulphonic acids, with a highly refined hydrocarbon lubricating oil composed mainly of saturated hydrocarbons and suitable for use as a steam cylinder oil, said per centage being suflicient to cause emulsification but insufficient to deposit ash when said mixture is injected into the cylinders of a steam engine, said soap stabilizes the oil against decomposition in presence of water vapor at temperatures as high as 500 F. I

2. The process of claim 1 in which the polyvalent metal is calcium and the range of soap is from .01% to 1.0%.

- ARTHUR LAZAR.

JOSEPH V. CRENNA.- 

